Different line constructions work better for certain applications on your sailboat than others. Matching the line construction to the type of rigging it's best suited for will make the line perform better and feel better to use.
Single Braid
Characteristics:
- Supple & flexible
- Doesn't absorb twists or kink
- Comes in two styles:
- Performance single braid: Made from very low-stretch fibers for extreme loads
- Blended/Polyester single braid: Soft and easy to grip, built for sheets and other hand-adjusted control lines
Double Braid
Characteristics:
- Braided core inside a braided cover
- Strong, durable, smooth-running line
- Easy to handle
Three Strand
Characteristics:
- Three strands twisted clockwise in a right-hand lay with fibers in each strand twisted left
- Favored on traditional boats
- Best for anchoring, towlines and mooring applications because it stretches significantly more than braid
There are a lot of line types out there. These guidelines make it easy to find the right type for different applications on your boat.
Performance Single Braid
Best Uses:
- Cascades & purchase systems
- Sportboat/performance backstay and runners
- Low-stretch and high-strength applications
Example Lines:
Performance Double Braid
Best Uses:
- Headsail halyards controlling low-stretch sails that cannot tolerate creep or stretch
Example Lines:
Dyneema Core Double Braid
Best Uses:
- Low-stretch sheets, halyards, and controls
Example Lines:
Blended Core Double Braid
Best Uses:
- Economical upgrades from stretchier polyester for club racers and performance cruisers
- Customized fiber blend offers low stretch, reduced weight, good handling, and reasonable cost
Example Lines:
Blended and Polyester Single Braid
Best Uses:
- Use for sheets and hand-adjusted controls
- Knobby or fuzzy textures are easy to grip and make lines easier to handle
Example Lines:
Dinghy Double Braid
Micro-Sized High-Tech Double Braid
Best Uses:
- No-stretch lashings
- Micro-sized purchase systems
- Control lines
Example Lines:
Polyester Double Braid
Best Uses:
- Sheets, control lines and halyards on cruising boats
- Handheld control lines on all types of boats
- As durable covers over high-tech cores where they encounter cleats, clutches or winch drums
Example Lines:
Micro-Sized Polyester Braid
Best Uses:
- Utility cords
- Flag halyards
- Tiedowns
- General lashing
Example Lines:
Anti-Chafe Covers
Best Uses:
- Use for heat- and abrasion-resistant protection on high-tech cores where they wrap around winches or pass through clutches
Example Products:
Three-Strand Line
Best Uses:
- Running rigging on traditional boats
Example Lines:
The Maximum Working Load (MWL) is the load that a block, line or other piece of gear can handle without excessive friction or permanent deformation. It is usually 50% of the the gear's breaking strength. Follow these tips to understand how load on the lines on your boat change and how to make sure your lines are sized correctly.
What Determines the Working Load of a Line?
Greater working loads are achieved by increasing line diameter or by using a line of the same diameter made from stronger fibers. 3mm V-12 single braid has a breaking strength of 2,100 lbs. 3mm HTS-90 single braid has a breaking strength of 3,400 lbs. Same diameter — 62% more strength.
Keep this in mind when choosing lines for your boat.
Static vs. Dynamic Loads
Static loads:
Sustained, steady forces like the tension in a halyard holding a fully hoisted sail in steady conditions.
Dynamic loads:
Transient, impact-type forces like the sudden jerk when a flogging sail fills abruptly, or the shock when a block comes taut after momentary slack.
Dynamic loads can multiply the effective load on a fitting by 2× or more compared to the equivalent static load.
For all running rigging and safety equipment: design the system for steady-state loads, then verify that the MWL of every fitting provides adequate margin for the dynamic loads your boat will actually experience.
How Purchase Systems Multiply Load
A purchase system (a block and tackle arrangement) multiplies the force a crew member can apply to a line — but it also multiplies the load on every fitting in the system. A 4:1 purchase pulling on a sheet with 50 lbs. of hand force produces 200 lbs. of output force. The block at the load end of the system must handle the full 200 lbs. plus friction losses.
The critical fitting in most purchase systems is the turning block at the load end, which carries the combined load of both the incoming and outgoing parts of the line. In a simple 2:1 purchase, this block carries twice the load of the single line leaving it. Always size the turning block and anchor point for the full system output load, not just the line load at the crew end.
How much stretch you can tolerate in your lines is mostly dependant on the type of sails you have and what kind of sailing you do on your boat. Follow these guidelines to pick the right ones for you:
Racing sailors flying low-stretch sails need low-stretch, high-modulus line. The trade-off is cost, lower durability, and less UV resistance.
Cruisers and daysailors with Dacron sails don’t need exotic high-tech line and benefit from the durability and UV resistance of polyester.
Acceptable stretch also depends on the application for both racers and cruisers. Genoa sheets and frequently adjusted hand-trimmed lines can tolerate more stretch. A halyard for a roller-furling jib that stays in place all season requires low-stretch line to prevent luff sag as the sail loads up.
Stretch is determined by fiber type and construction. Understanding the fibers is the key to selecting line that meets your needs at the lowest cost.
Different lines fibers have different characteristics that make them more or less suitable for different applicatios on your boat. Follow these guidelines to get the right line fiber for the job:
Nylon
- Almost never used in running rigging but is great for anchoring and docking where its stretch (up to 15%) absorbs shock loads
- Durable, with excellent internal and surface abrasion resistance
- High strength-to-weight ratio
- Absorbs water and shrinks, with a 10–15% strength loss when wet
Polyester
- Stretchier than newer fibers but with great abrasion resistance and UV resistance
- An excellent cover for double braid lines, protecting low-stretch cores from UV and chafe
- Works well for frequently adjusted lines like main and jib sheets, or moderately loaded control lines
- Very flexible, easy to handle, and still the preferred choice for most applications on cruisers and club racers
- Does not float
Polypropylene
- Light, relatively inexpensive, and relatively stretchy
- Frequently blended with other fibers like Dyneema to add bulk for easy handling
- Stronger and lighter than polyester but less costly than pure Dyneema.
- Floats and doesn’t absorb water, but has poor UV resistance.
- Works well for sheets, particularly light-air spinnaker sheets, dinghy sheets, and frequently adjusted control lines
- Requires replacement more often than polyester
Dyneema (High-Modulus Polyethylene / HMPE)
- Highest strength-to-weight ratio, low stretch, and impressive maximum working loads
- Very slippery with good hand, but poor knot-holding ability and a low melting point (300°F)
- Does not absorb water but experiences gradual “creep” or permanent elongation under sustained static load
- An excellent core upgrade from polyester double braid, with almost no stretch
- Often used uncovered, or with a polyester cover where it contacts cleats or winch drums
- Great in multi-part purchase systems, for replacing 7×19 wire in trapeze lines, and wherever light weight and low stretch matter
- Floats
Vectran (Liquid Crystal Polymer)
- Almost no stretch, no creep, and absorbs little water
- Works reliably at a high percentage of breaking strength, making it excellent for highly loaded applications
- Among the strongest core materials available
- Moderate UV resistance and durability
- Often used for upwind sail halyards under static loads like permanently hoisted roller-furling headsails, and for highly loaded purchase systems, travelers, and other no-stretch applications
Technora (Aramid)
- Very low stretch and no creep
- Like Kevlar, Technora has poor internal abrasion tolerance, fair chafe resistance, and is damaged by UV light
- Blending with another fiber — such as Dyneema SK-78 in the core of T-900 — reduces durability problems while preserving strength
- Needs protection with a polyester cover or core coating if stripped
PBO (Zylon)
- Polybenzoxazole is a rigid isotropic crystal polymer with extraordinary tensile strength — the best strength and stretch characteristics of any available fiber
- Low internal abrasion resistance, degrades rapidly in UV light, and loses approximately 15% of its strength when exposed to moisture
- Requires complete sealing from the elements. Extremely expensive and used only at the highest level of Grand Prix sailing
